1. Field of the Invention
Sensitizers for photopolymerizable compositions, the sensitizers being .alpha.,.beta.-unsaturated ketones based on 9,10-dihydro-9,10-ethano(or propano)-anthracene; and the photopolymerizable compositions comprising said sensitizers.
2. Description of the Prior Art
Use of sensitizers to extend the photosensitivity of photopolymerizable compositions into the visible region of the spectrum and to increase the speed of polymerization is known. Baum et al., U.S. Pat. No. 3,652,275, disclose selected bis(p-dialkylaminobenzylidene) ketones as sensitizers to enhance the efficiency of hexaarylbiimidazole initiator systems in photopolymerizable compositions.
Dueber, U.S. Pat. No. 4,162,162 discloses photopolymerizable compositions comprising a photopolymerizable monomer, an initiator, e.g., a hexaarylbiimidazole, and a sensitizing amount of a selected compound derived from aryl ketones and p-dialkylaminoaryl aldehydes.
Neither U.S. Pat. No. 3,652,275 nor U.S. Pat. No. 4,162,162 suggests the sensitizers of this invention, the most preferred of which are derived from 9,10-dihydro-9,10-ethanoanthracene disclosed in U.S. Pat. No. 2,406,645 (Thomas).